Vulnerability of deep neural networks for detecting COVID-19 cases from chest X-ray images to universal adversarial attacks

Under the epidemic of the novel coronavirus disease 2019 (COVID-19), chest X-ray computed tomography imaging is being used for effectively screening COVID-19 patients. The development of computer-aided systems based on deep neural networks (DNNs) has been advanced, to rapidly and accurately detect COVID-19 cases, because the need for expert radiologists, who are limited in number, forms a bottleneck for the screening. However, so far, the vulnerability of DNN-based systems has been poorly evaluated, although DNNs are vulnerable to a single perturbation, called universal adversarial perturbation (UAP), which can induce DNN failure in most classification tasks. Thus, we focus on representative DNN models for detecting COVID-19 cases from chest X-ray images and evaluate their vulnerability to UAPs generated using simple iterative algorithms. We consider nontargeted UAPs, which cause a task failure resulting in an input being assigned an incorrect label, and targeted UAPs, which cause the DNN to classify an input into a specific class. The results demonstrate that the models are vulnerable to nontargeted and targeted UAPs, even in case of small UAPs. In particular, 2% norm of the UPAs to the average norm of an image in the image dataset achieves >85% and >90% success rates for the nontargeted and targeted attacks, respectively. Due to the nontargeted UAPs, the DNN models judge most chest X-ray images as COVID-19 cases. The targeted UAPs make the DNN models classify most chest X-ray images into a given target class. The results indicate that careful consideration is required in practical applications of DNNs to COVID-19 diagnosis; in particular, they emphasize the need for strategies to address security concerns. As an example, we show that iterative fine-tuning of the DNN models using UAPs improves the robustness of the DNN models against UAPs.Comment: 17 pages, 5 figures, 3 table

教員研修充実方策の視点

発表・3,教員養成・研修の再構築-大学と教育委員会との連携,課題研究2,IV 課題研

Simple black-box universal adversarial attacks on deep neural networks for medical image classification

Universal adversarial attacks, which hinder most deep neural network (DNN) tasks using only a single perturbation called universal adversarial perturbation (UAP), are a realistic security threat to the practical application of a DNN for medical imaging. Given that computer-based systems are generally operated under a black-box condition in which only input queries are allowed and outputs are accessible, the impact of UAPs seems to be limited because well-used algorithms for generating UAPs are limited to white-box conditions in which adversaries can access model parameters. Nevertheless, we propose a method for generating UAPs using a simple hill-climbing search based only on DNN outputs to demonstrate that UAPs are easily generatable using a relatively small dataset under black-box conditions with representative DNN-based medical image classifications. Black-box UAPs can be used to conduct both nontargeted and targeted attacks. Overall, the black-box UAPs showed high attack success rates (40–90%). The vulnerability of the black-box UAPs was observed in several model architectures. The results indicate that adversaries can also generate UAPs through a simple procedure under the black-box condition to foil or control diagnostic medical imaging systems based on DNNs, and that UAPs are a more serious security threat

Knee Joint Thrust During the Early Stance Pahse of Gait Cycle

This paper is performed to evaluate with the knee joint motion of the active flexion (without weight bearing motion) and of the early stance phase during gait cycle (with weight bearing motion) by using a three-dimensional knee motion analysis system and the biomechanical pathogenesis of osteoarthritic knee is also discussed. Assessments were practiced about the knee motion of eighteen female patients with osteoarthritic knees; the controls were sixty-five volunteers of the adult healthy group including thirty-four males and thirty-one females. Typical motion patterns of active flexion and of early stance phase during gait cycle were evaluated to detect the difference based on osteoarthritis levels and gender. In results of this study, changes of adduction and internal rotation were appeared in the knee motion pattern during active flexion and early stance phase during gait cycle. During the active flexion, the mean values of adduction angle during flexion were 0.38±0.22 degrees in male group(MG), O.18±0.28 degrees in female group(FG) and 0.29±0.21 degrees in osteoarthritic knee group(OAG). On the other hand, in the early stance phase, the mean values of adduction angle during flexion were 0.29±0.21 degrees in MG, and were 0.29±0.27 degrees in FG and 0.87±0.48 degrees in OAG. During weight bearing motion of OAG, adduction angles increased to 0.58 degrees in the osteoarthritic knee, remarkably, that should mean as a phenomenon of the knee thrust. The thrust of OAG might be related to the joint laxity, deterioration of power in the quadriceps femoris muscle, the problem of their body weight and of aging. In the present study, the biomechanical pathogenesis of an osteoarthritic knee would be discussed about factors of osteoarthritic knee and be presented a few sources of knee osteoarthritis of femal quantitatively

Role of the silkworm argonaute2 homolog gene in double-strand break repair of extrachromosomal DNA

The argonaute protein family provides central components for RNA interference (RNAi) and related phenomena in a wide variety of organisms. Here, we isolated, from a Bombyx mori cell, a cDNA clone named BmAGO2, which is homologous to Drosophila ARGONAUTE2, the gene encoding a repressive factor for the recombination repair of extrachromosomal double-strand breaks (DSBs). RNAi-mediated silencing of the BmAGO2 sequence markedly increased homologous recombination (HR) repair of DSBs in episomal DNA, but had no effect on that in chromosomes. Moreover, we found that RNAi for BmAGO2 enhanced the integration of linearized DNA into a silkworm chromosome via HR. These results suggested that BmAgo2 protein plays an indispensable role in the repression of extrachromosomal DSB repair

Nonlinear Sigma model method for the J1-J2 Heisenberg model: disordered ground state with plaquette symmetry

A novel nonlinear sigma model method is proposed for the two-dimensional J1-J2 model, which is extended to include plaquette-type distortion. The nonlinear sigma model is properly derived without spoiling the original spin degrees of freedom. The method shows that a single disordered phase continuously extends from a frustrated uniform regime to an unfrustrated distorted regime. By the continuity and Oshikawa's commensurability condition, the disordered ground states for the uniform J1-J2 model are plaquette states with four-fold degeneracy.Comment: 4 pages (including 2 figures

Clinical Safety Assessment of Autologous Freeze-Drying Platelet-Rich Plasma for Bone Regeneration in Maxillary Sinus Floor Augmentation: A Pilot Study

The purpose of this clinical study is to evaluate the safety and preliminary efficacy of autologous freeze-drying platelet-rich plasma (FD-PRP) on bone regeneration in maxillary sinus floor augmentation as a preliminary pilot study. Five patients that required sinus floor augmentation to facilitate the placement of dental implants participated in this clinical study. The PRP was prepared from the autologous peripheral blood and was lyophilized and stored at −20 °C for 4 weeks before surgery. At surgery, triple-concentrated FD-PRP (x3FD-PRP) mixed with synthetic bone grafting materials was rehydrated following the transplantation into the sinus floor. The primary outcome was a safety verification of x3FD-PRP, evaluated in terms of the clinical course and consecutive blood tests. The secondary outcome was clinical efficacy focused on bone regeneration in sinus floor augmentation evaluated by radiographic examination and implant stability. There were no adverse events, such as systemic complications, excessive inflammatory reactions, severe infection, or local site healing complications, besides those on the usual course associated with surgery. Vertical augmented height was maintained, and the initial stability of implants was achieved post-operatively in 6 months. The results obtained in this study suggest that x3FD-PRP can be used safely for bone engineering in clinical practice. Further studies are required to draw a conclusion concerning the efficacy of x3FD-PRP since this was a pilot study with a single arm and a small sample size